Beacon transmitter



1949- c. J. DE DE LA SAB LONIERE 2,478,463

BEACON TRANSMITTER Filed July 28, 1947 INVENTOR\ Chfisfiaan Tu; de Lussanef dela. S'abloniere ATTOR/Vfj Patented Aug. 9, 1949 UNHTED sures BEACON TRANSMITTER.

Christiaan Jan de Lussanet de la Sablonire,

I Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Comp'any,Hartford,

Conn, as trustee Application July 23, 194 7, Serial No. 764,217- In the Netherlands February 19, 1946 Section 1, Public Law 690, August s, 1946 Patent expires February 19, 1966 4 Claims. 1

This invention relates to a beacon transmitter having a directional aerial system constituted by at least two radiators vertically arranged at a mutual distance and an intermediate horizontal line.

An aerial system of this kind substantially transmits rays which are polarised vertically and with the aid of which a course plane is characterised. As is well-known, as a result of the presence of earth, a field component polarised horizontally also occurs in the course plane, which component may lead to errors in the indication. Several means have previously been suggested for avoiding such errors in indication. These known means frequently have for their purpose to neutralise or to compensate the horizontally polarised field components but the so-called earth currents or screen currents themselves, which bring about the components, are not suppressed by the said means.

According to the invention, the field component polarised horizontally is reduced by providing between the aerial system and earth a layer of material having the capacity of absorbing ultrashort waves. The presence of this layer interferes with the interfering action of earth and brings about damping of the horizontally polarised waves, which otherwise would be transmitted as a result of this action.

The required dimensions of the said layer are dependent on the horizontal dimensions of the aerial system and on the nature of its constitutive substance.

The invention does not reside in the use of a particular type of absorbent material, various materials being known which absorb ultra-highfrequency waves, but rather in the use of an absorbent layer in cooperation with radiator elements to provide an antenna system having a desired radiation characteristic.

The thickness of the layer is dependent on the composition of the substance. If the absorption of the layer appears to be insufiicient, the layer may be given a greater thickness, if desired, until the desired result is obtained. The horizontal dimensions are required to be at least equal to those of the aerial system.

If the aerial system, instead of being arranged on the surface, is placed on an elevation, such as a building, the layer is required to cover this building.

The invention will be explained more fully by reference to the accompanying drawing showing, by way of example, one embodiment thereof.

The aerial system shown in the figure is constituted by two radiators l and 2 which are vertically arranged at a mutual distance and realised as dipoles. The radiators are fed in anti-phase with the aid of a screened transmission line 3 originating from a transmitter 4.

According to the invention, for the purpose of suppressing the horizontally-polarised radiation brought about by the horizontal part of the transmission line, a layer 5 of material having the capacity of absorbing ultrashort waves is provided between the aerial system and earth.

The invention is also applicable with advantage to other aerial systems, for example to a system constituted by a vertical radiator excited continuously and two reflecting vertical radiators which are arranged on each side thereof and are made operative alternately.

What I claim is:

l. A beacon transmitter having a directional aerial system and comprising at least two radiators vertically arranged at horizontally spaced positions above earth and transmission line means horizontally disposed above earth and intermediate said two radiators, said line feeding said two radiators in phase opposition, wherein between the aerial system and earth provision is made of a layer of material having the capacity of absorbing ultrashort waves and the horizontal dimensions of which are at least equal to those of the aerial system.

2. An ultra-high-frequency directional antenna system adapted to radiate vertically polarized waves comprising a pair of vertical dipoles positioned in horizontally spaced relation above ground, a horizontal transmission line disposed above ground intermediate said radiators and arranged to feed said dipoles in phase opposition, and a horizontal mat interposed between said dipoles and ground and having horizontal dimensions at least encompassing said dipoles, said mat being constituted by material which absorbs ultra-high-frequency radiation.

3. An ultra-high-frequency directional antenna system adapted to radiate vertically polarized waves comprising a pair of vertical dipoles, a

shielded transmission line supported horizontally above ground, said dipoles being supported at either end of said line and fed by said line in phase opposition, and a horizontal mat interposed between said dipoles and ground and having horizontal dimensions at least encompassing said dipoles, said mat being constituted by material which absorbs ultra-high-frequency radiation.

4; An ultra-high-frequency directional antenna system adapted to radiate vertically polarized waves comprising a pair of vertical dipoles,v a shielded transmission line supported horizontally above ground, said dipoles being supported at either end of said line and fed by said line in phase opposition, and a horizontal mat interposed between said dipoles and ground and having horizontal dimensions at least encompassing said dipoles, said mat being constituted by material which absorbs ultra-high-frequency radiation, said mat having a thickness at which the horizontal polarization component of dipole radiation is substantially eliminated.

CHRISTIAAN JAN DE LUSSANET DE LA SABLONIEE.

4 REFERENCES CITED UNITED STATES PATENTS Number Name Date 2,293,839- Linder Aug. 25, 1942 2,424,968 Busignies Aug. 5, 1947 2,433,369 Kandoian Dec. 30, 1947 2,436,578 Korn et a1 Feb. 24, 1948 FOREIGN PATENTS Number Country Date 706,417 Germany May 26, 1941 

